1. Field of the Invention
The present invention relates to an inkjet printing apparatus and a control method thereof.
2. Description of the Related Art
There are some cases where a printing apparatus of an inkjet method performs processing such as water repellent treatment on a surface (hereinafter also called “ejection opening surface”) on which ejection openings are provided for ejecting inks. In a case where the ink inhomogeneously adheres to the periphery of the ejection opening in the inkjet printing apparatus, in some cases at the time of ejecting inks, the ejected ink is pulled by the ink having adhered to the periphery of the ejection opening to shift an ejection direction of the ink. Therefore such treatment is performed.
In regard to the treatment to the ejection opening surface, in many cases the water repellent treatment is performed. However, recently in the environment where the function of the water repellent treatment is difficult to be sufficiently effective, such as a case of using pigment ink or high-function ink, or in the environment where a viscosity increase of ink in the ejection opening is easy to occur, such as a case of ejecting small liquid droplets, in some cases hydrophilic treatment is also performed. For example, Japanese Patent Laid-Open No. 2001-105599 discloses a print head in which such an ejection opening surface is coated with a material having super hydrophilic properties, thus performing the hydrophilic treatment thereon.
In such an ejection opening surface having hydrophilic properties, the ink of a thin-film exists across the entire ejection opening surface. Therefore, a difference in wet properties between the adhered ink and the hydrophilic surface is difficult to occur, and since the sufficient ink exists on the ejection opening surface, the ink in the ejection opening is difficult to dry.
Incidentally, recently the inkjet print head aims for imaging with higher quality and higher speeding in printing. Therefore an arrangement density of the ejection openings is becoming very high, for example, 600 dpi to meet conditions of small-liquid droplet formation and high-frequency drive.
As ink is ejected by the print head in which the arrangement density of the ejection openings is high and which has the ejection opening surface of the hydrophilic properties, the ink that has spread out across the entire ejection opening surface remains in the periphery of the ejection opening to overflow, and the ink accumulates in the periphery of the ejection opening. As a result, the ink in the periphery of the ejection opening blocks the ejection opening in some point of time, in some cases non-ejection of the ink is generated during the printing. As the non-ejection is generated during the printing, an image defect is possibly generated in a case where the ink of s single color is in use, and unevenness in density is possibly generated in an image in a case where inks of plural colors are in use.